IN THIS ISSUE: Mariah Carey's First Time Mother Nerves

Finally nearing the end of her pregnancy, Mariah Carey has been forced to slow down to ensure the safe arrival of her long-awaited twins. “Mariah has found the last eight weeks of her pregnancy quite hard,” a source close to the singer tells OK! in the new issue — on sale everywhere now! “She’s constantly tired, she’s been confined to her bed often and she hasn’t been able to work.”OK! NEWS: NICK CANNON GIVES MARIAH CAREY BABY UPDATE — “WE’RE HAVING TWINS!”

With so much time on her hands, Mariah, 41, is filled with anxiety, despite husband Nick Cannon’s reassurances. She has shelved her desire for a natural birth in favor of a doctor-recommended C-section, a second pal of the superstar tells OK!: “Mariah knows that a lot can go wrong during the delivery, and while she is trying to think positive and patiently follow doctors’ orders, she can’t help but have fears that something will go wrong.”

Even though “Nick’s been amazing at taking care of her,” according to the source, Mariah knows their nearly three-year marriage will face a big test when their son and daughter arrive. “Nick is 11 years younger — and at an age where he loves to hang out,” says another insider. “With babies in the house, there are going to be a lot of changes.”

FOR MORE ON MARIAH’S PREGNANCY, PICK UP THIS WEEK’S ISSUE OF OK! – ON SALE EVERYWHERE NOW!